LONDON – Former Vice President Joe Biden insisted Wednesday that he had not decided whether to challenge Donald Trump for the presidency in 2020.

"I am not a candidate at this point," Biden told USA TODAY after a speech at Chatham House, a London-based global affairs think tank.

Biden passed on an opportunity to run for president after the death of his 46-year-old son, Beau, from cancer in 2015. His name emerged at the top of lists of potential Democratic contenders for president in 2020, along with former New York City Mayor Michael Bloomberg and Sens. Cory Booker, Kamala Harris and Kirsten Gillibrand.

In London, Biden said he was not planning to run against Trump. But he didn't rule it out, saying he "had not made any decisions at this point." Biden has said he would decide by January whether to run.

A Morning Consult-Politico poll over the summer concluded that Biden would beat Trump in a hypothetical matchup in the 2020 presidential election.

Biden predicted in London that the Democratic Party would win control of the House of Representatives and the Senate in next month’s midterm elections, a contest he characterized as "a battle for the soul of America."

"I predict to you that the Democrats will win 40 seats in the House. I also think there is a better than even chance we win the Senate," he said in a Q&A after his address.

President Trump writes in an op-ed for @USATODAY on Wednesday that “the centrist Democratic Party is dead.” Reacting to that, former Vice President Joe Biden, who hasn’t confirmed whether he’ll run in 2020, told me in London just now: “Tell Trump he should hang on” #Breakingpic.twitter.com/GxIXY118r8

In a wide-ranging address that covered the United States' "special relationship" with the United Kingdom, as well as the encroaching threats of a more geopolitically assertive China and Russia, Biden said the world was at a "crossroads of competing values," and "looking inward, turning inward has never, ever worked for us before."

Though Biden did not mention Trump by name, he said a "siren call of phony nationalism" challenges "seven decades of the U.S. underwriting global security" as certain political actors treat "alliances like protection rackets."

Trump has exited or upended trade pacts, withdrawn from the Iran nuclear agreement, abandoned the Paris climate change accord and exacerbated tensions with European Union and North Atlantic Treaty Organization (NATO) allies.

“Open societies are not self-sustaining,” Biden said. “The system requires constant maintenance.” He said the world is at an “inflection point” and there is a "contest for the future."

"I have never seen Europe so uncertain and the U.S. in so much doubt," Biden said, referring to Britain's impending departure from the 28-nation EU political bloc, the rise of populist, right-wing governments across the region and intense cultural and political wars at home that span the economy, courts, immigration and gender relations.